1. Field of the Invention
The present invention relates generally to semiconductor packages, and more particularly to a semiconductor package having corners which are reinforced in a manner reducing occurrences of chip-out in the package body of the semiconductor package, and a method of manufacturing such semiconductor package.
2. Description of the Related Art
Semiconductor dies are conventionally enclosed in plastic packages that provide protection from hostile environments and enable electrical interconnection between the semiconductor die and an underlying substrate such as a printed circuit board (PCB) or motherboard. The elements of such a package include a metal leadframe, an integrated circuit or semiconductor die, bonding material to attach the semiconductor die to the leadframe, bond wires which electrically connect pads on the semiconductor die to individual leads of the leadframe, and a hard plastic encapsulant material which covers the other components and forms the exterior of the semiconductor package commonly referred to as the package body.
The leadframe is the central supporting structure of such a package, and is typically fabricated by chemically etching or mechanically stamping a metal strip. A portion of the leadframe is internal to the package, i.e., completely surrounded by the plastic encapsulant or package body. Portions of the leads of the leadframe extend externally from the package body or are partially exposed therein for use in electrically connecting the package to another component.
In the electronics industry, hand held portable applications such as cell phones, PDA's (Personal Digital Assistants), Bluetooth, and IMT2000 require semiconductor packages which are progressively smaller and lighter, yet of increasing performance. In many of the above-described conventional semiconductor packages wherein portions of the leads are partially exposed within the package body, such leads are typically included along only the peripheral edge of the package body. To meet the requirements of current hand held portable applications, the semiconductor packages used therein must have higher electrical performance and functionality, and thus increased numbers of leads which are electrically connectable to an external device. Although it has been suggested in the prior art to narrow the pitch of the leads formed at the periphery of the bottom surface of the package body to increase the number of leads, there are physical limitations in narrowing the lead pitch during the manufacture of the leadframe. Also, excessive narrowing in the lead pitch gives rise to a susceptibility of solder shorting between the leads when the semiconductor package is connected to an external device through the use of solder.
Other currently known semiconductor package designs provide increased number of leads by arranging the leads on a common surface of the package body in multiple rows and columns. However, the manufacturing methodology associated with such semiconductor package designs typically involves the completion of a sawing process wherein a saw blade is advanced completely through portions of the leadframe and partially into portions of the package body of the semiconductor package. More particularly, the advancement of the saw blade through portions of the leadframe effectively electrically isolates such portions from each other in a manner facilitating the formation of multiple columns and rows of leads. However, as a result of the sawing or singulation of the leadframe to facilitate the formation of the leads, the saw blade must necessarily cut into the package body as well. In this regard, the sawing process often gives rise to occurrences of chip-out or cracking in one or more of the four corners of the package body (which is typically square or rectangular), such chip-out or cracking being attributable to stress being concentrated on the four corners of the package body.
In those semiconductor package designs wherein multiple sets of leads are arranged to extend fully or partially about a die pad of the leadframe, a punch (as opposed to a saw) singulation process is sometimes used during the fabrication of such semiconductor packages to separate adjacent semiconductor packages arranged in a matrix from each other, a saw singulation process still being employed to electrically isolate portions of the leadframe from each other in a manner defining multiple sets of the leads. Similarly, in semiconductor package designs which include only a single set of leads extending fully or partially about the die pad of the leadframe, a punch singulation process is often employed as an alternative to a saw singulation process to effectively separate adjacent semiconductor packages arranged in a matrix from each other. When punch singulation is employed, the punch is typically configured such that each of the four corners of the package body is chamfered as a result of the punching operation. However, in the punch singulation process, the magnitude of the impact applied to the four corners of the semiconductor package attributable to the physical friction between the punch or singulation tool and the encapsulant material which forms the package body still results in occurrences of chip-out and cracking in the corners of the package body. In certain instances, the leads of the semiconductor package disposed in close proximity to each of the four corners of the package body may be completely separated from the package body as a result of the punch singulation process. The present invention addresses the chip-out and cracking problems that frequently arise as a result of the completion of punch and/or saw singulation processes on the package bodies of semiconductor packages which include either a single set or multiple sets of leads. More particularly, in accordance with the present invention, each of the four corner regions of the semiconductor package is reinforced to prevent the above-described occurrences of chip-out and cracking. These and other features of the present invention will be described in more detail below.